Honda BFP60A will not exceed 3800 rpm

[Oldone88]

Just got back from a test ride and it runs exactly the same, 3800 rpm Max. I could not find anything about a feedback loop on the trim limiting rpm. I ran another compression test and it was all good. It starts and idles good, when I put it in gear it seems to vibrate more than I would like, possibly because the idle seems to a bit low. Once you move the throttle and increase rpm to 900+ it smooths out. I may get into adjusting the idle at some point, but currently more concerned with top end rpm.

 

[MattFL]

Out of curiosity, will it rev past 3800rpm in neutral, or in gear with the prop removed? The goal is to figure out if the ECU is limiting the RPM for some reason, as opposed to just not making the power to pull past 3800rpm while pushing the boat.

 

[Oldone88]

Out of curiosity, will it rev past 3800rpm in neutral, or in gear with the prop removed? The goal is to figure out if the ECU is limiting the RPM for some reason, as opposed to just not making the power to pull past 3800rpm while pushing the boat.

I have not tried that. Is it ok to remove the prop and put it in gear on a water hose? I ended up pulling the injectors and taking them to a guy to be cleaned and flow tested. Initial report from him is that one of them wasn’t acting right. He was going to reclean them and I should have them back by Monday evening. I’ll either take it to the water and test, or possibly pull the prop and see what kind of RPM it will run with no load. I’m always worried about putting these outboards “in gear” out of water for some reason. Thanks

 

[ahicks]

In gear wouldn't be the issue with no prop. It would be over revving, especially with no load on it. When talking an issue occurring over 3800 rpm, I'm going to say that may be a bad plan.

 

[Oldone88]

That’s what I was leaning towards. I don’t have a whole lot of experience with marine engines in general, but I always assumed that you wanted a load on them when shifting. Thus I never do it out of water. I’m open to whatever opinions or experience is out there. It would be a way to determine if the engine itself is limiting its RPM.
I believe the rpm limit for the engine is about 6000 rpm. If I stayed below that it should be safe I guess? The place I purchased it from said they usually see about 5800 rpm.

 

[ahicks]

I mess with a lot of 40's and 50's. Because they sound so busy at 6k, I generally set them up for a target of 5.5k or so.

 

[MattFL]

It should be OK to briefly run it up to 4000 or 4500 just to see if it will do it, just don't keep it there for long. I wouldn't go full throttle to see how high it goes or anything, just briefly ease it up past 3800 then back to idle. If the computer is limiting it to 3800 then you'll know right away because it will stop at 3800, as soon as you're past 3800 then test over.

Just for a data point; mine is a 1999, year round use in salt. It's propped to spin 6k with a light load and with the boat loaded it spins about 5700 max. Typically cruising is 5000-5500 depending on how much of a hurry we're in, often for 30+ minutes (it has spent a lot of time >5000) and it has been doing this happily for more than 20 years. These things are designed to spend time at higher RPM and they're surprisingly durable, I really wouldn't worry about a few seconds at 4500 without a prop.

 

[Oldone88]

Got the injectors back. Report from the mechanic was that one had a horrible spray pattern. After cleaning them, they flowed and sprayed correctly. He said he didn’t think the improper spray pattern was enough to cause the rpm limiting I’m seeing. He didn’t have Any suggestions as to what to look at further, his suggestion was to hook it up for diagnostics to verify sensor operations.
As you can guess most marine places around here are running on about a 6 week waiting list, so I’m guessing that won’t be anytime soon.

I have company for the next week so I’ll probably have the boat on the water. Will be able to see if the injectors cleaning helped at all. After they are gone I’ll probably pull the prop and see if the RPM will reach into the 5k range. I’ll report back. I really appreciated all of the suggestions and help.
Thanks

 

[ahicks]

Re: the prop, you can try smaller. Results might be interesting. My bet is though, your problem lies elsewhere.

Did you ever verify the tach readings? Seems like somebody at the place you bought this should be able to help you out there.